1. Field of the Invention
The present invention relates to a turbocharger in which a lubricating oil is supplied to a bearing hole.
2. Related Art
There has heretofore been known a turbocharger having a turbine shaft rotatably held on a bearing housing, the turbine shaft having a turbine wheel provided on one end and a compressor wheel on the other end. Such a turbocharger is connected to an engine, and exhaust gas emitted from the engine rotates the turbine wheel. Also, the rotated turbine wheel rotates the compressor wheel through the turbine shaft. Thus, the turbocharger compresses the air by the rotation of the compressor wheel, and delivers the compressed air to the engine.
The bearing housing has a bearing hole penetrating in an axial direction of the turbine shaft, and a bearing part is disposed in the bearing hole. A lubricating oil is supplied to the bearing hole from outside the bearing housing. The lubricating oil lubricates the turbine shaft and the bearing part. The lubricating oil lubricates the bearing part and is then discharged to the outside of the bearing hole from both ends of the bearing hole. Japanese Patent Application Laid-Open Publication No. 2009-127437, for example, describes a configuration in which an oil drain passage is provided on a turbine wheel side of a bearing hole and a lubricating oil after lubricating a bearing part is discharged through the oil drain passage. This patent document also describes a configuration in which an oil passage of a cooling oil for cooling (cooling oil passage) is provided in the bearing housing and the cooling oil cools the turbine wheel side of the bearing housing under high temperature.
The cooling oil passage is provided on the turbine wheel side in the bearing housing, and is circularly formed radially outside the oil drain passage of the lubricating oil. A lubricating oil after lubricating a bearing part (radial bearing) on the compressor wheel side and a lubricating oil after lubricating a thrust bearing disposed on the compressor wheel side, for example, are guided to the cooling oil passage.